Paper based molding composition and process for making same



June 25, 1968 l W. C. COOPER PAPER BASED MOLDING COMPOSITION AND PROCESSFOR MAKING SAME Original Filed June 1, 1967 .fC/PAP PAPER Wan da C.Coo/o er l N VEN TOR B Y QoQfP-k mm United States Patent O 3,390,003PAPER BASED MGLDNG CMPOSXTION AND PRQCESS FOR MAKING SAME Wmda C.Cooper, Midland, Tex.

(3032 Wroxton, Houston, Tex. 77005) Continuation of application Ser. No.460,207, June 1, 1967. This application Oct. 2, 1967, Ser. No. 672,395 4Claims. (Cl. 106-193) ABSTRACT GF THE DESCLGSURE This invention isdirected to a dry paper-based molding composition having paper fibers ofa size up to l/i inch in maximum dimension as the major constituentthereof, and the sodium salt of carboxy-methyl-cellulose as the bindingagent. Such composition may be extended with an inert material such asmolding plaster for economy in applications where the accompanying lossof strength is acceptable. The material offers advantageous moldingcharacteristics, strength, economy and durability.

My invention relates to a dry paper-based molding composition which,upon the addition of water in the proper amount, may be used as amolding material having particular utility in the tield of arts andcrafts as well as other commercial and industrial uses.

Materials which are used in molding various objects, both useful andornamental, include papier-mache, molding clay of various types andcompositions, and similar materials which are plastic when wet, andpresent a relatively smooth surface when dry. My invention involves amaterial of this type which is superior to other materials of which I amaware because of its molding characteristies, strength, economy anddurability. It also offers certain other advantages as will bedescribed.

My invention involves reducing scrap paper to tibers of relatively smallsize, and mixing them with a water solule cellulose gum of the typeidentified by the trademarks AKU-CMC, and DRSCOSE, both beingessentially the same material. If desired, molding plaster or talc maybe added. The resulting dry material is quite stable and easy to handle,and it may be stored for long periods of time with only normal moistureprotection. The addition of a measured amount of water and a relativelybrief and simple mixing operation produce an unusually high grade ofmolding composition. Thus, the use-r is provided with a light and easilyhandled dry material which is readily available in any desired amount.When an occasion for its need arises, the proper amount of water isadded. With a slight amount of mixing, as by kneading within a flexible,impervious bag, the material is quickly ready for use.

In accordance with the foregoing, it is a principal object ot myinvention to provide a process for preparing a dry paper-based moldingcomposition which can be made ready for any use by the addition ofwaterin the appropri-ate amount.

It is a further object of my invention to provide a dry paper-basedmolding composition of unusually high quality which can be convenientlypackaged and transported and will retain its useful properties despitelong periods of storage.

My process is illustrated in the attached drawing in which the singlefigure is a flow diagram showing the steps involved in practicing oneexample of my invention.

The first step is to reduce the paper to small particles or fibers.Economy suggests the use of scrap paper, and although any grade ot paperis suitable, it will be apparent that the better grades of scrap papersuch as that used in ithd Patented .June 25, 1968 ice slick papermagazines will produce a product of higher quality.

The means for reducing the paper to a brous condition is wholly optionalbut the product of the grinding or shredding operation should range insize from a conditic-n much like powder or dust up to approximately 1/4inch maximum dimension. The distribution of particle sizes over thisrange is not critical.

I have found that particles which Will pass through a ls inch screen areparticularly suitable for use in the fields of arts and crafts. lt isapparent that the smaller or more nely divided particles will producematerial having a ner texture, whereas the employment of largerparticles will result in a coarser texture.

have found a conventional hammer mill to be a particularly suitablemeans for reducing paper to the proper condition for use in my process.A mesh screen at the point of exit from the mill will confine thematerial until it is of proper size.

The material identified as AKU-CMC or Driscose is added to the paperlibe-rs following completion of the grinding step. This product is thesodium salt of carboxy-methyl-cellulose, and is sold under the trademarkAKU-CMC by Algemene Kunstzijde Unie of Arnhem, Holland, and under thetrademark Dricose by Philips. Such material is commercially available intwo grades, Technical and Purilied, and although I prefer to use theTechnical grade, either can be made to produce a useful moldingcomposition. Technical grade AKU- CMC contains certain salts which havebeen removed from the Purilicd grade. Unless otherwise indicated, theterm carboxy-methyl-cellulose as used herein will identify thecommercially available Technical grade.

The res-.sons for the unique utility of carboxy-methylcellulose in apaper-based molding composition are only partially understood at thistime, but such material lends itself to ready distribution throughoutthe paper fibers, accepts water readily and the resulting product hassuperior molding properties.

Dry molding plaster (hydrous calcium sulfate) or talc (acid magnesiummetasilicate) may be added to the mix if desired. Such materials improvethe consistency of the molding composition when moist, and the surfacetexture of the molded product. They also reduce shrinkage and warping.However, they cause a reduction in strength, and normally would not beused when maximum strength is desired.

A reasonably high quality and high strength molding composition isproduced when the paper bers and Technical gradecarboxy-methyl-cellulose are combined in a weight ratio of approximatelysix units of paper for each unit of carboxy-methyl-ccllulose. A weightratio of paper to Technical grade carboxy-methylcellulose in excess often to one las a substantial adverse cli'ect on the quality of theresulting material and a weight ratio of less than two units of paperfor one unit of Technical grade carboxy-methyl-cellulose has a similarconsequence. Wholly satisfactory results for most commercial uses areobtained when the weight ratio of paper to Technical gradecarboxy-rnethyl-cellulose is held in the range of not more than eight toone and not less than four to one. Within the ranges indicated, strengthincreases with the amount of carboxy-methyl-cellulose, but as the costdoes the same, it is preferable to hold the amount ofcarboxy-methyl-cellulose to the minimum level consistent with thestrength required.

For art and hobby work where high strength usually is not a requirement,a quality product will result from the addition of 4 parts by weight ofan inert filler material such as dry plaster or talc to the 6 to 1mixture of paper fibers and carboxy-methyl-cellulose. A similar amountof filler may be added throughout the ranges specified with nosignificantly adverse affect on any property except strength. Asindicated above, a better finish texture and less shrinkage is producedby the use of a filler material such as plaster or talc.

As previously mentioned, the purified grade of carboxy-methyl-cellulosewill produce a result comparable to that of the six to one ratio forTechnical grade material when the ratio of paper tocarboxy-methyl-cellulose is approximately thirteen and one-half to one.How ever the relatively small amount of carboxy-methylcellulose requiresmore attention to mixing in order to achieve even distribution, so Iprefer the Technical grade.

It is essential that the paper fiber and carboxy-methyl cellulose bemixed to substantial homogeneity. A large blender in the form of aninverted cone in which the paper and carboxy-methyl-cellulose areintroduced and agitated by circulating air has proven to be suitable,but other means, including mixing by hand, serves equally well.

The dry material may be sacked in conventional kraft paper bags or otherconvenient and economical packaging means. I have found that these bagsprovide a quite satisfactory protection against moisture during normalstorage conditions.

The material produced by my method assumes a cOnsistency much like clayupon the addition of approximately four to five units of Water for eachunit of the dry mix, by weight, as determined by the degree ofplasticity required. If plaster or talc is present, somewhat less watermay be required. After molding to any desired shape, the material willdry within a few days, or even less if it is exposed to a small amountof artificial heat.

When dry, the material becomes surprisingly hard and tough. It may besanded to produce a smooth surface, and it may be sealed and painted.Although there is a small amount of shrinkage during drying, onlyrelatively thick applications of material require special provisions forsuch shrinkage, and for normal uses, the shrinkage will not beperceptible.

A specific working example of the method of my invention and the productresulting therefrom would begin with a convenient amount, say 100 poundsof scrap paper of magazine quality. This paper is shredded in a hammermill and removed through a 1/s inch screen to insure that no particlesare larger than 1/s inch in maximum dimension. The paper fibers will belight and fluffy, and it is convenient to transport them to acentrifugal blender by a current of moving air.

The carboxy-methyl-cellulose and plaster may be introduced to the paperfibers prior to entry into the blender. For 100 pounds of paper,approximately sixteen and onehalf pounds of Technical gradecarboxy-methyl cellulose produces a quality product. At the same timeapproximately sixty-seven pounds of molding plaster are added. The paperfibers, carboxy-methyl-cellulose and 4 v plaster are agitated by aircurrents Within the blender to achieve an homogeneous mixture, and theproduct can be removed and packaged when mixing is completed.

The process described hereinabove is wholly suitable for preparing thedry material in its basic form. In addition, fireprooting agents, fastdrying additives, wetting agents, and special aggregates such as mica,sand, or other materials may be added to the dry product for specialeffects or requirements. It is necessary only that such additionalmaterials be well mixed with the paper fibers andcarboxy-methylcellulose and that they display no excessive aflinity formoisture which would adversely affect the dry storage characteristics.

Various modifications of my material and process will occur to thoseskilled in the art. It is my desire to protect by patent all suchchanges and modifications which fall within the scope of the followingclaims.

I claim:

l. A diy paper-'based molding composition comprising a substantiallyhomogenous mixture of one unit weight of carboxy-methyl-cellulose,approximately four unit weights of a dry material selected from theclass consisting of hydrous calcium sulphate and acid magnesiummetasilicate, and from two to ten unit Weights of dry paper fibers of asize not exceeding one-quarter inch in maximum dimension.

2. A dry paper-based molding composition comprising a substantiallyhomogenous mixture of one unit Weight of carboxy-methyl-cellulose,approximately four unit weights of a dry material selected from theclass consisting of hydrous calcium sulphate and acid magnesiummetasilicate, and from four to eight unit weights of dry paper fibersranging in size from powder to particles not exceeding one-quarter inchin maximum dimension.

3. The process of making Aa dry paper-based molding compositioncomprising the steps of reducing paper to paper fibers ranging in sizefrom powder to one-quarter inch maximum dimension, blending one unit 'byWeight Of dry carboxy-methyl-cellulose with approximately four units byweight of a dry material selected from the class consisting of hydrouscalcium sulphate and acid magnesium metasilicate, and mixing the blendedmaterial With from two to ten units by weight of the dry paper fibers toa condition of substantial homogeneity.

4. The process of making a dry paper-based molding compositioncomprising the steps of shredding paper to reduce it to a substantiallyfibrous condition, passing the shredded paper through a 1A; inch screen,blending one unit by Weight of dry carboxy-methyl-cellulose withapproximately four units by Weight of a dry material selected from theclass consisting of hydrous calcium sulphate and acid magnesiummetasilicate, combining the blended material with from four to eightunits by Weight of the dry paper fibers, and mixing the combination to acondition of vsubstantial homogeneity.

No references cited.

JULIUS FROME, Primary Examiner.

